Blocks, for example paving elements, facade elements, sand-lime blocks, concrete blocks, bricks or vitrified bricks, natural stones and the like, are often subjected to subsequent treatment, irrespective of the nature of their material, in order to lose their artificial appearance.
Particularly frequently, freshly produced, set concrete blocks, in particular concrete paving slabs, are subjected to such subsequent treatment, in the course of which the surfaces and/or the edges are distressed or broken, in order to adapt the appearance to that of natural stones. For this purpose, the concrete blocks are introduced in relatively large numbers into a rotating drum, where they are “rumbled”, the surfaces and edges of the blocks striking against one another and the blocks treated in this way leaving the drum in an “aged” state. Such an apparatus is known from DE-A 29 22 393.
When concrete blocks are treated in a rotating drum, surfaces and edges which are not even visible, for example when the aged blocks are used in paving, are also worked. To this extent, energy and time are unnecessarily wasted. Furthermore, for shipping purposes it is necessary to arrange the concrete blocks which have been treated and have left the rotating drum in a regular arrangement on a pallet, which requires an inordinate amount of work and time.
The prior art discloses a process, which is an alternative to the rotating drum, in which the blocks to be aged are placed together with distressing bodies onto an inclined channel. This channel is made to vibrate, so that the blocks strike against one another and against the distressing bodies. As a result, the blocks are given an aged appearance, which corresponds approximately to the result of the rotating drum described above. On account of the inclination of the channel, the blocks to be worked and the distressing bodies travel from an upper end to a lower end of the channel. Once the blocks and the distressing bodies have left the channel at its lower end, the distressing bodies are separated from the blocks. The distressing bodies are fed back to the upper end of the channel, while the blocks are conveyed further to a sorting device.
The prior art discloses for the sorting of the blocks, sorting installations which appropriately align the blocks and arrange them in pallet form. Such sorting installations cause high procurement and operating costs and also have a corresponding space requirement.
DE 36 21 276 C2 discloses a process in which concrete blocks are applied as a single layer in regular arrangement to an underlying surface in the form of a panel. Subsequently, the exposed surface and the adjoining exposed edges, or essentially only the edges, of the concrete blocks are distressed in an irregular manner by means of a vibrating striking or distressing device.
This process makes it possible to dispense with a subsequent sorting device, since the layer of blocks as they are produced is not changed. Before being worked with the striking or distressing devices, the blocks are pushed together on the underlying surface in the form of a panel and aligned, so that the blocks lie close together and there are no longer any intermediate spaces between them. The distressing tools of the distressing device are arranged on a movable carriage, which takes them over the surfaces of the blocks, so that the free surfaces and the upper edges of the blocks are distressed in an irregular manner by the distressing tools.
A disadvantage of this process, however, is that the blocks aged in this way look as though they have been artificially worked and not naturally aged. An ideal edge rupture of the blocks, as produced by the rumbling of the blocks in a rotating drum, is not obtained by using the process of the congeneric document.
EP 0 860 258 B2 discloses an apparatus and a process in which the blocks are arranged in one or two layers, preferably in the layer in which they are produced, between two elements, preferably plates. In this arrangement, the lower plate, on which the concrete blocks rest, is in operative connection with a vibration device. The vibration device is used to bring the blocks into movement, so that they are moved back and forth between the plates. As this happens, the blocks strike against one another and against the upper and lower plates, whereby the edges are broken on the upper side and underside. Furthermore, the upper sides and undersides of the blocks are distressed by the respectively assigned plates. The vertical side edges of the concrete blocks and the side faces are broken or distressed by the respectively adjacent concrete blocks.
It has been found in tests that the edge rupture is much worse the larger the size of the block to be aged. This is a result of the fact that the distressing angle is all the more shallow the larger the size of the block lodged between the plates. The shallow distressing angle results in unfavorable rupture of the edges.
In a way analogous to the ageing process by means of the rotating drum, there is, in this case, the disadvantage that surfaces and edges of the blocks which are possibly not visible are worked, resulting in energy and time being unnecessarily wasted. In addition, the necessary working time, in particular in the case of set concrete blocks, is high and the edge rupture is not ideal.
The present invention is, therefore, based on the object of providing a process and an apparatus for artificially ageing blocks, in particular concrete blocks, vitrified bricks and natural stones, whereby energy- and time-saving ageing is possible with an advantageous edge rupture.